Refraction techniques using modified streak retinoscope assembly

ABSTRACT

Techniques and retinoscopic apparatus for measuring or determining a patient&#39;s optical error are disclosed. The techniques include overrefraction and can be performed from a fixed position, avoiding the practitioner&#39;s need to move back and forth relative to the patient&#39;s eye. Equipment associated with the apparatus is adapted to record the location of the retinoscope slide (relative to its upper or lower position) during the examination to provide information concerning the optical error present in the patient&#39;s eye.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.07/893,245 (now U.S. Pat. No. 5,285,224), filed Jun. 3, 1992, entitled"Methods and Apparatus for Determining Refractive Error," whichapplication is a continuation-in-part of application Ser. No. 07/526,395(now U.S. Pat. No. 5,120,124), filed May 21, 1990, entitled "Devices forDetermining the Crossed Cylinder Powers and Axes for Multiple LensSets," which application is a continuation-in-part of application Ser.No. 07/427,724 (now U.S. Pat. No. 5,104,214), filed Oct. 27, 1989,entitled "Trial Frames, Adjustable Spectacles and Associated LensSystems," which application is a continuation-in-part of applicationSer. No. 07/310,334 (now U.S. Pat. No. 4,943,162), filed Feb. 13, 1989,entitled "Astigmatic Self-Refractor and Method of Use," whichapplication is a continuation-in-part of application Ser. No. 07/116,322(now U.S. Pat. No. 4,840,479), filed Nov. 2, 1987, entitled "CrossedCylinder Lenses Refractor with Three-lens Variable Crossed CylinderAssembly and Method of Use," which application is a continuation-in-partof application Ser. No. 07/023,980 (now U.S. Pat. No. 4,820,040), filedMar. 16, 1987, entitled "Crossed Cylinder Lenses Refractor and Method ofUse," which application is a continuation of application Ser. No.06/670,398(now abandoned), filed Nov. 9, 1984, all of which applicationsare incorporated herein in their entireties by this reference.

FIELD OF THE INVENTION

The present invention relates to apparatus and methods for measuring ordetermining optical errors in the eyes of humans (or animals) and moreparticularly to techniques for doing so using a modified streakretinoscope.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 3,597,051 to Copeland, incorporated herein in its entiretyby this reference, illustrates an exemplary streak retinoscope assembly.One such commercial assembly, the "Optec 360" retinoscope 10 of FIG. 1,includes a thumb slide 12 adapted to move relative to the retinoscopeshaft. As shown in FIG. 2A, advancing slide 12 to its upper positioncauses the light rays emanating from the retinoscope to be approximatelyparallel. FIG. 2B, by contrast, illustrates the convergence of the lightrays that occurs when slide 12 is moved to its lower position.

Current refraction techniques use the streak retinoscope forneutralizing optical errors. Such techniques are described in, forexample, Videotape No. 5063 of the American Academy of Ophthalmology'sContinuing Ophthalmic Video Education series, entitled "Retinoscopy:Plus Cylinder Technique," and require use of a phoropter, trial frames,or additional lenses. According to these techniques, the slide of theretinoscope remains in the upper position throughout the retinoscopicprocess. Only if greater than one diopter of astigmatic error is presentdo these techniques suggest "enhancing" the patient's cylinder power bylowering the retinoscope slide. By contrast, "enhancing" the streak toestimate the sphere power does not occur.

After the practitioner neutralizes the patient's error by changing thephoropter or trial frame lenses, the values of those lenses areconsulted to determine the patient's ocular correction. These refractiontechniques essentially use the phoropter or trial frame lenses to makethe parallel light rays emanating from the retinoscope conjugate to thepatient's fundus. Doing so in turn causes the rays backscattered by thepatient's fundus to be conjugate to the practitioner's eye, permittingneutralization of optical error at a specified working distance.

According to Videotape No. 5063, prior retinoscopic estimatingtechniques were complex and thus rarely learned or used by the averagepractitioner. Such "two-handed" techniques require the practitioner torotate a collar or sleeve on the retinoscope while simultaneously movingthe slide up and down, effectively creating "spiral" movement of theslide and sleeve. To perform these techniques, moreover, thepractitioner must move back and forth relative to the patient, therebyalternately approaching and receding from the eye under examination. Thepatient's optical error is then typically estimated based on the widthof the focused streak of light emanating from the retinoscope as seen bythe practitioner on the patient's retina. Following "straddling" andother movements of the streak, the patient's cylindrical error axis canultimately be estimated by comparing the longitudinal axis of the streakto a scale on the phoropter. Moreover, as discussed on page 21 of Dr. J.C. Copeland's manual for "Steak Retinoscopy" printed by Optec, Inc.(which manual is incorporated herein in its entirety by this reference),these prior estimating techniques were "best . . . perform[ed] . . . onthe naked eye" and thus did not involve overrefraction of existingprescription lenses.

SUMMARY OF THE INVENTION

The present invention provides retinoscopic techniques for measuring ordetermining a patient's optical (sphere and cylinder) error. Unlikeprior methods, the present techniques can be performed from a fixedposition, avoiding the practitioner's need to move back and forthrelative to the patient's eye. They also need not involve straddling andcan be performed whether or not the patient is wearing existingprescription glasses.

During the examination, equipment connected to the modified streakretinoscope of the invention senses the position of the slide relativeto some nominal location (e.g. its upper or lower position), providinginformation concerning the optical error present in the patient's eye.This information can be used to calculate the resulting power andcylinder axis of appropriate corrective lenses. By contrast with priorretinoscopic techniques, the present invention uses this positionaldisplacement of the lamp filament from the fixed condensing lens withinthe retinoscope to permit the rays emunating from the device to beconjugate to the patient's fundus.

The Optec 360 retinoscope 10 of FIG. 1 contains a +20.00 D condensinglens 14 and a bi-pin lamp 16. When slide 12 is in its upper position(FIG. 2A), the filament of lamp 16 is approximately five centimetersfrom condensing lens 14. The rays emanating from the filament passthrough lens 14 as essentially parallel, therefore, thereby focusingthose rays at infinity. Displacing slide 12 from its upper positionconverges the emanating rays relative to condensing lens 14 according tothe formula:

    P=D+(d×D×d)-W

where

P=total vergence power of retinoscopic light rays at the patient's pupil(in diopters)

D=vergence power of emerging retinoscopic light rays (in diopters)

d=distance from the patient's pupil at which retinoscopy is performed(the "working distance") (in meters)

W=working distance (in diopters)

In the slide's lower position on the Optec 360 retinoscope 10 (FIG. 2B),the lamp filament is approximately 6.6 centimeters from condensing lens14. Accordingly, displacing slide 12 of retinoscope 10 can generatedioptric power ranges as shown below for various (exemplary) workingdistances:

    ______________________________________                                        Working Distance   Generated Powers                                           (centimeters)      (diopters)                                                 ______________________________________                                         0.0               0.00    to +4.83                                            2.54              -39.40  to -33.98                                          10.0               -10.00  to +2.83                                           20.0               -5.00   to +4.50                                           25.0               -4.00   to +6.67                                           33.0               -3.00   to +9.50                                           50.0               -2.00   to +12.59                                          66.0               -1.50   to +18.80                                          100.0              -1.00   to +26.00                                          ______________________________________                                    

By measuring the slide's displacement from, e.g., its upper position,therefore, information concerning the optical power generated using theretinoscope can be obtained at various times during the examination(including when the streak fills the pupil). Embodiments of the modifiedstreak retinoscope of the present invention use a momentary switch andpotentiometer connected to the retinoscope to convert this slidedisplacement quantity into an electrical resistance. This resistance canin turn be measured and used to calculate the optical power necessary tocorrect the patient's error. The calculation can be performedelectronically by a computer adapted to receive the resistance value,for example, permitting the computer to determine the optical correctionneeded for an overrefracted patient merely by appropriately combiningthe resistance with the patient's current prescription.

Other embodiments of the apparatus of the present invention canincorporate lens discs or carriers permitting substitution of otherpower lenses for the +20.00 D condensing lens included in the Optec 360retinoscope 10 of FIG. 1. Alternatively, the powers of these additionallenses can be combined with that of the condensing lens, or the slidedisplacement can be increased, to enhance the dioptric range of thedevice. Because the operating principles of some commercial retinoscopesare opposite those of the Optec 360 (i.e. focusing light rays atinfinity when the slide is down), yet other embodiments of the inventionfunction exactly opposite the manner described above.

It is therefore an object of the present invention to provide refractiontechniques using a streak retinoscope.

It is another object of the present invention to provide refractiontechniques that can be performed by a practitioner from a fixed positionrelative to a patient.

It is also an object of the present invention to provide overrefractiontechniques using a streak retinoscope.

It is a further object of the present invention to provide equipmentconnected to a streak retinoscope that senses the position of theretinoscope slide relative to some nominal location (e.g. its upper orlower position).

It is yet another object of the present invention to provide a streakretinoscope connected to a momentary switch and potentiometer forconverting slide displacement into an electrical resistance.

It is an additional object of the present invention to provideelectronic means for converting the sleeve displacement value (andpatient's existing prescription if overrefraction is performed) into aresulting optical correction for the patient's eye.

Other objects, features, and advantages of the present invention willbecome apparent with reference to the remainder of the text and thedrawings of this application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational, partially cut-away view of an Optec 360retinoscope.

FIG. 2A-B is a schematic representation of the light rays emanating fromthe Optec 360 retinoscope of FIG. 1 with the slide in its upper position(FIG. 2A) and lower position (FIG. 2B).

FIG. 3 is an elevational, partially schematicized view of a modifiedretinoscope of the present invention.

FIG. 4 is a cross-sectional view of the modified retinoscope taken alonglines A--A of FIG. 3.

FIG. 5A-I are selected "streak" images possibly viewed using themodified streak retinoscope of FIG. 3.

FIG. 6A-D are additional streak images possibly viewed using themodified streak retinoscope of FIG. 3.

DETAILED DESCRIPTION 1. Apparatus

As referenced above, FIG. 1 shows an Optec 360 retinoscope 10 havingthumb slide 12, condensing lens 14, and lamp 16. Lamp 16 includes alinear filament designed to create the "streak" reflex or reflectionseen by the practitioner from the retina of the eye of the patient beingexamined. Slide 12 moves approximately 1.6 cm along handle 18 so that,in its upper position, the filament of lamp 16 is approximately 5.0 cmfrom lens 14, which has power of +20.00 D. In its lower position,therefore, the filament of lamp 16 is approximately 6.6 cm from lens 14.

In use, light rays emanating from lamp 16 are reflected by mirror 19approximately 45° into the patient's eye. The practitioner can view therays backscattered from the patient's retina through a small opening 20in mirror 19, effectively focusing the backscattered rays into hispupil. In essence, the phoropter or trial frame lenses subsequentlyplaced before the patient are designed to place the patient's eye infocus with the practitioner's eye peering through opening 20.

FIGS. 3-4 illustrate a modified streak retinoscope 22 of the presentinvention. Retinoscope 22 may be a modified Optec 360 retinoscope 10(FIG. 1) or any other suitable device having a displaceable slide 24 orsome other means for moving a lamp relative to a lens. As shown in FIGS.3-4, retinoscope 22 includes a potentiometer 28 coupled to slide 24,providing means for converting displacement of the slide 24 along handle30 into an electrical resistance. This resistance can in turn bemeasured by ohmmeter 32 connected to potentiometer 28 and used by acomputer 36 or other appropriate mechanism to calculate the opticalpower necessary to correct a patient's error. Merely by appropriatelycombining the resistance measured by ohmmeter 32 with the patient'scurrent prescription using known equations, computer 36 can rapidly andeasily determine the optical correction needed for an overrefractedpatient.

FIG. 4 details the coupling between potentiometer 28 and slide 24. Wire40 directly attaches slide 24 to the recording wire or contact arm 44 ofpotentiometer 28 so that, as slide 24 is displaced (upward or downward)along handle 30, contact arm 44 moves in a corresponding manner.Accordingly, potentiometer 28 tracks movement of slide 24, indicatingits deviation from a nominal position. Those skilled in the art willrecognize that other means may be used to sense the position of slide 24along handle 30, including mechanisms electrically or optically coupledto slide 24 or uncoupled but otherwise capable of providing thenecessary information. A momentary switch 48 or other suitable devicemay be included as part of computer 36 (FIG. 3), retinoscope 22, orelsewhere in the circuitry to provide means for indicating the point atwhich the practitioner determines that a displacement measurement needsto be recorded.

2. Exemplary Operations

To refract a patient's eye using retinoscope 22, the practitioner needmerely assume a (fixed) position a known distance (e.g. 50 cm) from thepatient.

For a patient having a solely spherical error between approximately-1.75 D and +2.75 D, for example, activating retinoscope 22 with slide24 in its upper position initially provides to the practitioner thestreak reflexive image shown in FIG. 5A. Because no astigmatic error ispresent in this example, neither the width nor intensity of the streakvaries as collar or sleeve 50 is rotated ±90° . Lowering slide 24 widensthe reflected streak (FIGS. 5B-C) until it fills the patient's pupil asillustrated in FIG. 5D. Again, because the patient has no astigmaticerror in this example, rotating sleeve 50 diminishes neither the widthnor intensity of the streak (FIG. 5E). At this point momentary switchmay be depressed, providing computer 36 information concerning thedistance slide 24 has been displaced from its upper position.

B.

For a patient having a (solely) spherical refractive error of -2.00 D, aretinoscope 22 located 50 cm from the patient's eye, and slide 24 in itsupper position, the practitioner will initially view the images of FIGS.5D-E. Accordingly, no further refractive effort is needed and theinitial position of slide 24 is immediately converted into an electricalresistance and transmitted to computer 36.

C.

For a patient having a myopic (solely) spherical refractive errorgreater than -2.00 D, the images of FIGS. 5D-E are likely not attainablefor working distances of 50 cm or greater. To accommodate these largerspherical errors, the practitioner can place a phoropter or trial framelens of, for example, between -3.00 D and -12.00 D before the patient(or use the patient's existing prescription lens) and continue loweringslide 24 until the images of FIGS. 5D-E are obtained. Again, at thatpoint the practitioner can simply activate computer 36 to record thedisplacement information obtained through potentiometer 28. In thiscase, however, the power of the phoropter, trial frame, or existingprescription lens must be included in the final corrective calculation(either as a separate input to computer 36 or manually after thedisplacement information is converted into the refractive error).Alternatively, the practitioner can move toward the patient, decreasingthe distance between the retinoscope and eye under examination, until heviews the images of FIGS. 5D-E. This decreased working distance must bedetermined and appropriately factored into the value obtained fromcomputer 36, however.

D.

For a patient having a (solely) spherical error greater than ±12.59 D,the images of FIGS. 5D-E are similarly not likely to be obtained at aworking distance of 50 cm. The practitioner in such a case can place aphoropter or trial frame lens of, for example, between +3.00 and +12.00before the patient (or again use the patient's existing prescriptivelens). With this lens in place, the practitioner can continue loweringslide 24 until the images of FIGS. 5D-E are obtained, at which point hecan activate computer 36 to record the displacement information obtainedthrough potentiometer 28. As in connection with the prior example, thepower of the phoropter, trial frame, or existing prescription lens mustbe included in the final corrective calculation.

FIGS. 5F-I and 6A-D illustrate reflections viewed for a patient having acylindrical error in addition to the spherical errors mentioned inexamples A-D. In FIG. 5F-I, the axis of the patient's spherical error is180° , while in FIG. 6A-D the axis is 45°. For the patient having acylindrical error principally in the 180° meridian, the practitionerdetermines the spherical error in the same way as discussed above. Uponrotating sleeve 50 by ±90°, however the image of FIG. 5F is obtained andthe angular orientation of the streak (i.e. 180°) is noted or estimatedby the practitioner. The practitioner again lowers slide 24 (FIGS. 5G-H)until the streak fills the pupil (FIG. 5I), at which point computer 36is utilized to record the displacement of the slide 24. The notedcylinder axis can then be included with the measurements to produce afinal corrective prescription. Embodiments of retinoscope 22 can alsoincorporate lens discs or carriers to permit lenses of other powers tobe substituted for or combined with lens 14. For example, including adisc of spherical lenses in +0.50 D increments capable of beingoptically aligned with opening 20 would enhance the practitioner'sability to use retinoscope 22 accurately at any working distance from0-100 cm. Incorporating a distance finder into retinoscope 22 wouldadditionally permit electronic measurement of the working distance forinput into computer 36, while electrically or otherwise coupling thelens disc to the computer would allow direct input of the addedspherical power into the computer 36 for use in later calculations.

Other embodiments of retinoscope 22 function opposite the mannerdescribed earlier, recording, for example, the distance slide 24 isdisplaced from its lower position. These embodiments are designed toaccommodate the operating principles utilized in some commercialretinoscopes, in which the light rays from lamp 16 are focused atinfinity when slide 12 is completed lowered. Yet other embodiments ofretinoscope 22 contemplate permitting slide 24 to move more than 1.6 cm,providing a greater range of dioptric powers available for refraction.

The foregoing is provided for purposes of illustrating, explaining, anddescribing embodiments of the present invention. Modifications andadaptations to these embodiments will be apparent to those of ordinaryskill in the art and may be made without departing from the scope orspirit of the invention.

I claim:
 1. A method of refracting an eye having optical errorcomprising the steps of:a. providing a retinoscope comprising:i. ahandle; ii. a lamp housed within the handle; iii. a lens housed withinthe handle; and iv. a slide displaceable along the handle to move thelamp within the handle relative to the lens; b. providing means, coupledto the retinoscope, for sensing displacement of the slide along thehandle; c. illuminating the lamp; and d. displacing the slide along thehandle to refract the eye and sensing the slide displacement.
 2. Amethod according to claim 1 further comprising the step of calculatingthe optical error of the eye using the slide displacement sensed by thesensing means.
 3. A method to claim 2 further comprising the step ofplacing an existing prescription lens over the eye before displacing theslide along the handle.
 4. An optical instrument for use in examining aneye, comprising:a. a housing; b. a lens positioned within the housing;c. means, comprising a light source positioned within the housing so asto be moveable relative to the lens, for producing a streak of light;and d. means for sensing the position of the light source relative tothe lens during the examination.
 5. An optical instrument according toclaim 4 in which the housing comprises a slide coupled to the lightsource.
 6. An optical instrument according to claim 5 in which thesensing means is coupled to the slide.
 7. An optical instrument for usein examining an eye having optical error, comprising:a. a housing; b. alens positioned within the housing; c. a light source positioned withinthe housing so as to be moveable relative to the lens; d. means forsensing the position of the light source relative to the lens; and e.means, electrically connected to the sensing means, for determining theoptical error of the eye.
 8. An optical instrument according to claim 7in which the housing comprises a slide coupled to the light source. 9.An optical instrument according to claim 8 in which the sensing means iscoupled to the slide.
 10. A device for refracting an eye comprising:a. aretinoscope comprising:i. a handle; ii. a lamp housed within the handle;iii. a lens housed within the handle; and iv. means for moving the lamprelative to the lens; b. means, coupled to the moving means, for sensingmovement of the lamp relative to the lens; and c. means coupled to themovement sensing means, for determining the refractive error of the eye.11. A device according to claim 10 in which the movement sensing meanscomprising:a. means for providing a variable electrical resistancedependent on the sensed movement; and b. an ohmmeter, connected to thevariable electrical resistance providing means, for measuring thevariable electrical resistance.
 12. A device according to claim 11 inwhich the refractive error determining means comprises a digitalcomputer.
 13. A device according to claim 12 in which the variableelectrical resistance providing means comprises a potentiometer coupledto the moving means.